PHP has long been a favorite dynamic programming language for Web developers. After 10 years of growth, 2006 looks to be a banner year for the open source language as its collaboration framework, partner ecosystem and the language itself are expected to grow and gain new users.

Look for a confluence of three distinct branches of the PHP language, with versions 4, 5 and 6 all likely to be out in the market in 2006. It will also be a year in which PHP will continue to challenge .NET and Java as the online language of choice for developers.

According to data from Netcraft, over 22 million domains currently use PHP. A November study from SecuritySpace.com reports that PHP is actually the most popular Apache Web server module, with some 44 percent of all surveyed servers running it. By contrast, Perl, another popular open source language, comes in at 11 percent.

A Brief History of PHP

Like Java, PHP also celebrated its 10th birthday in 2005. Unlike Java though, PHP was not launched with much fanfare 10 years ago when Rasmus Lerdorf released it as "Personal Home Page Tools."

In 1997, two Israeli developers, Zeev Suraski and Andi Gutmans, added their skills to the open development language and helped write PHP 3. Suraski and Gutmans have since formed Zend Technologies, one of the lead commercial sponsors of PHP. They also helped to put out PHP version 4 in 2000 and PHP 5 in 2004.

But developers, especially open source developers, don't always jump to the newest versions of a language as soon as it's released; such is the case with PHP 5 as well.

"What is clear to us is that when you have 20 million domains running PHP 4 not everyone is going to go to their Web sites and upgrade right away," Gutmans said. "Almost 50 percent of the Zend customer base is running PHP 5 and there is huge momentum and adoption."

Ebay provides its Web Services API (define) to PHP users and has noticed a migration from users of PHP 4 to 5. Ebay evangelist Adam Trachtenberg said the shift has been gradual.

"In some cased 5 is better for us as XML (define) and SOAP (define) support in PHP 5 are much better than they are in PHP 4," Trachtenberg said.

A security incident earlier this year with PHP however led some to speculate at the time that PHP 4.x was more widely used and supported than PHP 5.x. In that incident, PHP 4 was fixed faster than PHP 5.

The Future: PHP 6

PHP 6 is likely to come out in 2006 with some important innovations. Perhaps the most important new feature is Unicode, an encoding scheme that allows for virtually all major world languages to be encoded into a single character set.

Ebay is bullish on PHP's embrace of Unicode. Trachtenberg said it would make it easier for developers to communicate with anyone across eBay's sites. Although no official group within eBay contributes to the PHP community, developers did "work with Zend to improve the PEAR/SOAP toolkit and then donated back to community, which helped eBay too," Trachtenberg said.

Three Versions: Triple Confusion?

Three versions of PHP in one year? Sounds like a recipe for confusion. Not quite, supporters say.

Hostway, a large Chicago based ISP, expects that it will support all three PHP versions when they are available.

"We make an effort to keep up with new versions of useful technology such as PHP while not abandoning those customers that still rely on older versions," a Hostway spokesperson said. Ebay doesn't see three PHP versions as an issue either.

Gutmans argued that three versions out at once is a sign of its strength.

"It's actually very much different than Microsoft, which forces people to upgrade," Gutmans said. "Over time there will be a natural migration and when too many people lose interest [in an older versio], it'll stop being maintained at some point," he continued.

"But the good thing is that it's open source, so if a company today has built their application on PHP 4 and wants to keep running that for the next ten years they will have the source code where they can maintain it themselves."